Pressure Sensor

Pressure sensor is the sensor to detect the pressure both positive pressure and negative pressure.Positive pressure is pressurized air generated by the compressor, while the negative pressure or vacuum is generated by air suction vacuum pump.

Analog Pressure switch
PGS10 by Wika

In the beginning, the pressure sensor is apressure gauge is an indicator of the pressure using the  needle(mechanical/analog). As the needs and developments of automation, pressure gauge is equipped with contact switch that function as a signal as pressure marker has reached the specified value. Until now, although many use the pressure switch has digital indicator, but the type with needle indicator or analog is still used.
However, for electronic or digital pressure switch has several advantages compared with analog type:

1. Accuracy, electronic type has high accuracy because it is supported by the electronic system without the influence of mechanical or phisical changes.
2. High speed response, of course electronic type has faster response because without the need to perform mechanical movements.
3. Life time, Electronic type has longer life time. Another case where analog type, mechanical movement will cause rapid deterioration component proportional to the time of usage.

As explained previously, pressure switch detect the positive pressure and negative pressure. Several types of pressure switch in the market such as production of Keyence or Omron capable of detecting both positive or negative pressure. Whereas some others only detect the positive pressure only, or vacuum only. Type with the ability to detect both are often reffered as pressure switch " compound type".
A pressure unit used on the pressure switch are, Pa, kgf/cm2, bar and Psi. With refference to the pressure unit, the following pressure switch categories are based on pressure area. As an example is the pressure switch made by Keyence ie type compound AP30W:

AP-C30W by Keyence

Pressure area categories:

1. Pressure switch(positive): 0 to +100.0 kPa
2. Compound/multirange : +101.3 to -101.3 kPa
3. Vacuum switch (negative) : 0 TO -101.3 kPa

Regarding other categories, some models based on application needs. Such as the type with separate sensor head and amplifier is widely used in many areas contains oil. And afor type with one package commonly used in clean area that electronic circuit on the amplifier will be safe.

Separated type AP-40
by Keyence

As the end of this chapter, output signal from this sensor is in the form of digital output (ON-OFF) or in the form of analog signal (4-20 mA). Some of the type posessed both, but there is also the only one of these functions.